259 Paper IX (iv) Design of Hydrodynamic Wavy Contacting Face Seals with Non-Newtonian Lubricants Z.S. Safar and T.A. Osman This paper presents an analytical study of mechanical face seals taking into consideration the effect of surface waviness. Given waviness, number of waves, geometry and sealed non-Newtonian fluid the model predicts the load supported by the fluid pressure, the frictional torque the leakage rate and the tilting moment for both parallel and tilted radial face seals. The modified pressure equation of a non-Newtonian fluid for a misaligned face seal with the film thickness representing wavy surface 1s solved numerically to obtain the pressure distribution and hence the seal performance characteristics. Using this model the effects of waviness, face width, tilt parameter and the fluid behavlour, index are examined. Based on these results certain conclusions are reached concerning the role of waviness in face seals for different types of non-Newtonian lubricants. 1 I NTRODUCTI ON Mechanical face seals are used to control fluid leakage in a wide range of industrial equipment. Earlier works have explained the mechanism of generation of pressure and load in mechanical face seals [ 1,2 1. Several authors have shown that hydrodynamic pressure larger than hydrostatic one is generated in the fluid film because of the effects of misalignment [31 and surface waviness t4,5,61. So far not much attention has been paid to the study of the role of the type of fluid used in view of the apparent differences in the stress and strain rate relations for non-Newtonian fluids. Sinha et a1 [71 have used the power law model to analyze hydrostatic pressure effects on misaligned radial face seals neglecting the effect of the circumferential shear rate. They found that the axial force is not greatly influnced by the viscometric constant n . Also they found that the tilting moment increases significantly with n while the lubricant leakage rate decreases as the viscometric constant increases . In this paper the power law model is used to analyse the pressure equation with non-Newtonian fluid. The effect of surface circumferential and radial waviness of a misaligned radial face mechanical seal is studied. In the present analysis various seal characteristics such as separating forces, tilting moment, frictional torque and lubricant leakage are obtained as function of tilt parameter, waviness amplitude, radii ratio and the viscometric constant . 1.1 C F FN GN hO hr HK he 'e h H m M nX n Y n N P P Q I r1 I0 R Notatlon a I0 tilting parameter C=- ho dimensionless frictional torque constant defined by equation (6) constant defined by equation (7) lubricant film thickness mean film thickness dimensionless film thickness H=h/ho radial amplitude film thickness dimensionless radial amplitude film thickness Hr= hr/ho circumferential amplitude film thickness dimensionless circumferential amplitude film thickness H,=he/ho viscosity constant dlmensionless moment ratio H-n !Ix dimensionless transverse moment dlmensionless restoring moment flow behavior index number of periods in the circumferential direction lubricant pressure dimensionless lubricant pressure dimensionless leakage rate seal radius seal inner radius seal outer radius dimensionless seal radius R=r/ro inner to outer radii ratio J